The United Auto Workers' recent failure to organize workers at the Chattanooga Volkswagen plant shows just how much unions need to change to stay relevant.

Unions represent about 11 percent of all U.S. workers, down from 20 percent two decades ago, and less than 7 percent of private sector employees. Only in state and local governments do unions hold sway, but that is accomplished by supporting politicians who accede to demands for excessive pensions and benefits that are driving many cities and states to financial ruin.

In the private sector, technologies have replaced many blue-collar jobs, and contemporary managers are much more sensitive to workers' needs than in earlier decades.

The South, where much manufacturing has relocated, remains decidedly ant-union, and labor leaders have cultivated much of the public animus.

Many autoworkers at the present day VW plant blame the recent bankruptcies of General Motors and Chrysler on the UAW's combative behavior. Hundreds of thousands of hardworking blue collar workers lost jobs at Detroit automakers and suppliers, as the union resisted changes in work rules and overly generous benefits that kept productivity below and labor costs above foreign-owned plants operating in the U.S. South

Also, many folks in Chattanooga see the UAW as modern-day carpetbaggers preying on their political freedom. Along with virtually all the unions affiliated with the AFL-CIO, the union strongly supports the Democratic Party, abortion rights, gun control, and other liberal causes.

Those positions may well suit northern civil service unions but are an anathema to many southern blue collar workers. They don't want to pay union dues to finance liberal activism and political campaigns.

Labor leaders have argued unfair employer tactics are responsible for a string of union defeats in plant representation elections. However, in Chattanooga, VW openly supported the UAW's organizing efforts and put a gag order on its managers, who being Southerners might have been inclined to criticize the union.

Granted Tennessee Republican politicians opposed the UAW—for example, claiming auto parts manufacturers would be reluctant to locate in the state if it went union. However, the AFL-CIO should expect no less when it has used dues collected from workers, regardless of their political preferences, to oppose the overwhelming majority of Republican candidates for public office since the days of Harry Truman.

Cynically, union leaders now advocate "reforms" in federal rules governing representation elections to shorten to 25 days the period between a union filing for a contest and the actual ballot. Such a change would have stifled workers inside the Chattanooga plant who opposed the UAW from mounting a meaningful communications campaign and exercising their right of free speech.

Also, the unions propose compelling employers to providing rosters of email addresses and other personal information. It would seem the AFL-CIO and Democratic politicians advocating rule changes have been consulting with the civil libertarians at the National Security Agency on privacy issues.

Unions would do better to burnish their image by becoming less confrontational and bipartisan. Continually badgering the Detroit Three to amend new arrangements that bring labor costs more in line with southern competitors and impeding the necessary restructuring of teetering municipal and state pensions systems are not helping their image.

Many workers unions would like to organize don't approve of financial support for radical feminist causes or President Obama's push for increases in minimum wages much above what is justified by inflation.

Simply, union leaders should give up on most social causes that have nothing to with their members' wages and work environment, cultivate genuine ties with moderate Republicans and let their members choose who to support in elections.

Workers join unions to improve their economic lot, not subvert the viability of their employers. And whatever each of us thinks about many social issues, workers don't join unions to dictate their moral choices in America's ongoing cultural wars.

Peter Morici is an economist and professor at the Smith School of Business, University of Maryland School, and a widely published columnist. He tweets @pmorici1